1. Field of the Invention
The present invention relates to a method for inducing neural differentiation of stem cells. In more detail, the present invention relates to a method for inducing neural differentiation of stem cells by inhibiting BMP (bone morphogenetic protein) and Activin/Nodal signaling pathway in the stem cells.
2. Background of Technique
BMPs (bone morphogenetic proteins) belong to a subfamily of TGF-beta (transforming growth factor-beta) superfamily. TGF-beta pathway plays a central role in diverse signal transduction pathways which regulate growth and differentiation in vertebrates and invertebrates. TGF-beta family is divided into two main groups: (a) BMP group, and (b) TGF-beta/Activin group. Initially, BMPs have been isolated as proteins inducing formation of bone and chondrocyte in a body, and then found to have many regulatory activities during morphogenesis of vertebrate and invertebrate development. Up to now, not less than 30 types of BMPs have been identified in a variety of species including Drosophila and C. elegans (Ducy P et al, The family of bone morphogenetic proteins. Kidney Int, 57 (6):2207-14 (2000)).
Although BMPs have been first found as proteins inducing formation of bone and cartilage in a body, various BMPs have a biologically critical activity in various types of cells including neural cells. For example, BMPs are associated with cell growth and differentiation, apoptosis, neuroectoderm and mesoderm formation, nerve system differentiation (e.g., testis, digestive organs, kidney, lung, teeth, etc.), and right-left asymmetry (Wozney 3M et al. The bone morphogenetic protein family: multifunctional cellular regulators in the embryo and adult. Eur J Oral Sci., 106: 160-6 (1998)).
Activin/Nodal (TGF-β superfamily member) signaling pathway is essential to retain pluripotency in human embryonic stem cells and mouse epiblast stem cells. In addition, Activin/Nodal signaling pathway is important to develop mesoderm in vertebrates.
Stem cells are a generic name for undifferentiated cells of a stage before differentiation toward each cell consisting of tissue, and then differentiated into specific cells by specific differentiation stimuli. Compared to cell division-arrested differentiated cells, stem cells have proliferation (expansion) characteristics capable of producing self-renewal cells via cell division, and may be also differentiated into other lineages by environmental or differential stimuli due to differentiation potential into specific cells by differentiation stimuli, suggesting that stem cells have plasticity to differentiation.
Recently, stem cells have been enormously focused on cell therapeutics. Practically, there have been actively executed many studies for stem cells as cell therapeutics for treating numerous neurological diseases caused by neuron damages. In particular, cranial nerve diseases have been supposed as the most suitable target for cell transplantation treatment than other diseases in the senses that cells externally transplanted are expected to be long-term survival since cranial nerve tissue exhibits almost no immunorejection unlike other tissues.
In this connection, there has been currently attempted to apply stem cells for treating a disorder such as stroke, Alzheimer's disease, Parkinson's disease, demyelinating disease and spinal cordinjury (Isacon O, Deacon T, Trends. Neurosci., 10: 477-482 (1997); Studer et al., Nat. Neurosci., 1: 290-295 (1998)).
Meanwhile, there has been urgently demanded on a technique to differentiate stem cells into specific cells in an effective manner to enhance clinical usefulness of stem cells as cell therapeutics.
WO 2005/003320 discloses a method for neural differentiation of stem cells, and in more detail, a method for inducing stem cells to differentiate into neural cells comprising the steps of: (a) culturing the stem cells with basic fibroblast growth factor; (b) culturing the cells of the step (a) with fibroblast growth factor 8 and Sonic Hedgehog; (c) culturing the cells of the step (b) with brain-derived neurotrophic factor; and d) co-culturing the cells of the step (c) with astrocytes. WO 2004/093812 discloses that a novel class of compounds having particular formula functions as potent inducers of neurogenesis in embryonic stem cells.
WO 2004/05308 discloses a method for preparing dopaminergic cells by interrupting TGF-β signaling pathway in stem cells.
Unfortunately, a technology with higher efficiency to differentiate all stem cells into specific cells (in particular, neural cells) has been not yet reported.
Throughout this application, various publications and patents are referred and citations are provided in parentheses. The disclosures of these publications and patents in their entities are hereby incorporated by references into this application in order to fully describe this invention and the state of the art to which this invention pertains.